1. Field of the Invention
This invention relates generally to screen printing and, more particularly, to an improved retractable registration system for aligning screen printing frames in a printing machine.
2. Description of the Prior Art
Many types of materials and products may be printed utilizing screen printing operations. Such screen printing operations may involve the printing of intricate designs utilizing a number of colors, requiring a high degree of precision. The use of more than one color results in the use of a number of screens, one for each color, with each screen being associated with an image in that color. It is necessary to ensure that the images for each screen are properly aligned so that when printed, the associated colors are aligned properly and that the final image is of high quality. Therefore, to provide the necessary precision in known printing machines, various types of registration systems are used to align each screen in registration to the platform on which an item is to be printed. This has become increasingly more important because of the multiple short runs printed on today's machines. Furthermore, since many types of items or materials are printed, such as caps, jackets, shirts, shorts, posters, etc., each bearing multi-colored designs printed in small quantities, there exists the need in the art for an accurate printing registration system, which may be easily and quickly used.
U.S. Pat. No. 5,503,068 to Newman discloses a retractable pallet attachment for screen printing. The system uses a pair of arms extending along longitudinal axes under an image platform. The arms have at least two cross sections, one of which is square and held in a mounting bracket. The mounting brackets are secured to the lower surface of the image platform, and the arms are movable in the mounting brackets to be extended outwardly from underneath the image platform. Each arm includes a finger extending therefrom, with at least one registration pin thereon for registration with an opening, or the like, in a screen frame. In the extended position, the arms are rotated to bring the fingers into a position 90.degree. from their rest position, for cooperation with the respective opening in a screen frame. The movable arms include a first detent means for retaining the arms in a retracted position, and a second, separate detent means for retaining the arms in exact registration positions for aligning the same with the openings in the screen frame. Although this attachment solves many problems, it tends to be complicated, includes a large number of moving parts, and requires separate components to allow the arms to be moved or translated in a first direction, and further means whereby the fingers and registration pins may be rotated into and out of their operating positions when in the registration position. Furthermore, the first and second detent means for retaining the arms in the different positions require numerous parts, adding further costs and complexity to the attachment.
U.S. Pat. No. 5,377,422 to Newman discloses a roller frame having alignment brackets with a hole and a slot formed therein for registration with a pair of pins to align the roller frame. This roller frame may be used with the pin registration means set forth in U.S. Pat. No. 5,503,068, discussed above.
Other registration systems for use with screen printing are set forth in U.S. Pat. Nos. 4,911,070 to Miske, 4,938,130 to Thorpe, 4,993,166 to Bradely, 5,094,160 to Jennings, 5,094,161 to Taylor, 5,188,026 to Fuqua et al., and 5,226,366 to Schlife. Each of these patents disclose various positioning means for use in aligning printing screens in a printing machine. However, none of these devices disclose a simple rotary-type registration system of the type set forth in the present application which may be easily and quickly moved into position, in a single motion, to aid in registration of sequential printing screen frames, or rotated, in a single motion, into a retracted position, out of the way under an image platform.
Therefore, although the registration systems disclosed and shown in the prior art, solve many of the problems with accurate printing of a workpiece on an image platform, and attempt to solve problems that occur because of the need to register multiple screens, there still exists a need in the art for a system that is more quickly and easily actuated, and which is easier and less expensive to make.